Two methods are typically used to modify the planar configuration of a piezoelectric material. One method is photolithographic processing. This method employs multiple processing steps, such as cleaning; metalization of a protective mask; photoresist application; developing and etching the protective mask; etching the piezoelectric material; and removal of the protective mask. This method is time consuming and greatly increases the cost of the etched piezoelectric material.
Another method is ion etching. This method requires aligning and securing the piezoelectric material to an inclined target plate, positioning and securing an aperatured protective mask over the piezoelectric material, and passing an ion beam from an ion source through the aperatures in the protective mask to etch the piezoelectric material along the aperatured configuration. This method is very slow, which greatly increases the cost of the etched piezoelectric material.
Various apparatus has been used for laser "scribing" or "dicing" a wafer or substrate. Reference U.S. Pat. Nos. 3,816,700; 3,991,296; 3,626,141 and 3,814,895. Diamond cutting tools, abrasive wheels, circular saws and lasers are typically used to physically remove a semiconductor material, such as silicone, or a dielectric material, such as alumina. Partial removal of material is often called "scribing," whereas cutting through such material is often called "dicing." Lasers have not typically been used to "scribe" or "dice" piezoelectric material, due to the anisotropic nature of the material. Twinning is induced in most piezoelectric materials by mechanical or thermal stress. This "twinning" acts to raise the inductance and effective resistance of the piezoelectric material as well as raising or lowering the frequency of the crystal, depending upon the type of piezoelectric material used. Reference is made to Laser Induced Twinning in Quartz by T. L. Anderson et al., published by Materials Research Laboratory, Pennsylvania State University, 1976.
Also known are various methods for aligning wafers or substrates, such as taught by U.S. Pat. Nos. 4,141,456; 4,182,024 and 4,046,985. These patents disclose mounting a wafer or substrate on an X-Y axis table, and controllably moving the X-Y axis table by means of a computerized control unit.